The present invention relates to a semiconductor circuit and a method of retrieving a signal to the semiconductor circuit. More specifically, the present invention relates to a semiconductor circuit as an input circuit capable of dealing with both a differential input method and a single input method, and a method of retrieving a signal to the semiconductor circuit.
In general, a liquid crystal display has been widely used. The liquid crystal display may be formed of a thin film transistor (a TFT) as a liquid crystal panel. Further, the liquid crystal display may be provided with a source driver as a drive circuit for displaying an image on the liquid crystal display. The source driver is configured as the drive circuit of the liquid crystal display for receiving a data signal and a control signal from a timing controller for displaying an image on the liquid crystal display, and to output the data signal and the control signal to a signal line of the liquid crystal display.
When the source driver outputs the data signal and the control signal, in order to prevent the liquid crystal display from being burned out, a polarity of an output terminal for outputting the data signal to the liquid crystal display is switched alternately. In other words, the output terminals with an even number are categorized as an EVEN, and the output terminals with an odd number are categorized as an ODD, so that each of the groups (the EVEN and the ODD) is controlled to output. In order to correspond to the output control, an input signal is categorized as the EVEN or the ODD.
The source driver is configured to receive the data signal and the control signal in the following two input methods, namely, a differential input method such as an RSDS input method and a single input method such as a COMS input method (refer to Patent Reference 1).    Patent Reference 1: Japanese Patent Publication No. 2005-338727
In the differential input method (the RSDS input method), an input circuit of a conventional source driver receives the data signal and the control signal in the following manner. The input circuit of the conventional source driver receives the EVEN signal at a timing when a clock (CLK) signal declines, and receives the ODD signal at a timing when the clock (CLK) signal rises.
In the differential input method, the conventional source driver has two types of input paths, that is a P terminal for receiving a P side input signal and an N terminal for receiving an N side input signal (for example, an inverted signal of the P side signal). Further, the conventional source driver is configured to determine an L level and an H level of the input signal according to a voltage difference between the P side input signal and the N side input signal. The P side input signal and the N side input signal tend to have a small amplitude, thereby making it possible to reduce a noise. On the other hand, it is necessary to provide the two input terminals (the P terminal and the N terminal) for receiving one single data.
In the single input method (the COMS input method), the conventional source driver receives the data signal and the control signal in a time chart shown in FIG. 7. FIG. 7 is the time chart showing an example of a data retrieving operation of the input circuit of the conventional source driver.
As shown in FIG. 7, in the single input method, the input circuit of the conventional source driver receives the EVEN signal at a first timing when the clock (CLK) signal rises, and receives the ODD signal at a next timing when the clock (CLK) signal rises.
In the single input method, the conventional source driver is configured to determine the L level and the H level of the input signal according to a voltage level of the input signal. Accordingly, it is necessary to provide only one input terminal for receiving one single data. On the other hand, the input signal tends to have a large amplitude, thereby increasing a noise as opposed to the differential input method.
In the conventional source driver, the differential input method or the single input method is selected according to an application. More specifically, it is necessary to design the input method of the conventional source driver according to the output method of the timing controller. The conventional source driver may be provided with the input circuit capable of adopting both input methods. In this case, the conventional source driver is configured to switch modes between the differential input method and the single input method, so that the conventional source driver is able to deal with both the differential input method and the single input method.
Patent Reference 2 has disclosed the conventional source driver having an input circuit capable of adopting the differential input method and the single input method.    Patent Reference 2: Japanese Patent Publication No. 2009-111794
In the input circuit of the conventional source driver, as explained above, it is necessary to provide two input terminals for inputting one single data in the differential input method, and to provide just one input terminal for inputting one single data in the single input method. The input circuit is configured to be capable of adopting both input methods through the following two configurations.
In the first configuration, the input circuit is provided with a differential input terminal provided for inputting the input signal in the differential input method, and is separately provided with a single input terminal for inputting the input signal in the single input method. In the second configuration, the input circuit is provided with a common input terminal provided for inputting the input signal in the differential input method and the single input method.
In the first configuration, it is necessary to provide a large number of input terminals, thereby increasing a chip size. In the second configuration, the input circuit has unused input terminals. Accordingly, it is necessary to design a specific configuration for the unused input terminals (for example, it is necessary to dispose an extra wiring portion on a substrate, or to fix the unused input terminals in a device). As a result, it is necessary to change a wiring pattern on the substrate depending on the input method. Further, when the input terminal is fixed, the P side input terminal has a load different from that of the N side input terminal, thereby causing a large influence on a characteristic of the conventional source driver in the differential input method.
In view of the problems described above, an object of the present invention is to provide a semiconductor circuit and a method of retrieving a signal to the semiconductor circuit capable of solving the problems of the conventional semiconductor circuit. In the present invention, it is possible to properly input an input signal input through a different input method according to the input method.
Further objects and advantages of the invention will be apparent from the following description of the invention.